I. Field of the Invention
My invention relates generally to the cutting and measurement of sheet materials during building construction. More particularly, the present invention relates to a system using disposable, snap-on guide clips for accurately marking sheet materials such as gypsum wallboard with the location of access holes for desired electrical and telephone outlet boxes and the like.
II. Description of the Prior Art
In modern construction a variety of generally planar, sheet like materials are used for constructing interior walls. Preformed drywall panels are placed over the interior framing to finish walls or ceilings after electrical prewiring. Those familiar with dry wall construction techniques will recognize that many different types of panels including veneers, particle board, sheet rock, or wallboard are common. Ordinarily the exterior and internal walls are first framed with suitable, spaced apart studs. The electrical wiring then proceeds. Various fixtures that house switches, electrical outlet plugs, and ceiling fixture connections, are mounted to the framing studs to safely terminate the conductors. Such fixtures and junction boxes include outlet boxes for A. C. power, cable television feeds, prewired telephone installations, intercom wiring, air conditioning vents, and the like. These outlet boxes are located to and extend through access openings formed in the covering members. The outlet boxes enable the final connections to be completed after wall panels are installed. Certain plumbing lines or fixtures may also be installed just after completion of the framing.
Modern outlet boxes are made of plastic or metal. They facilitate secure containment of the wires or pipes that are connected to the outlets or other terminal fixtures that are in turn mechanically fastened to the outlet boxes. Many outlet boxes are rectangular, although a variety of other shapes are in common use. They are placed at diverse and varied physical locations throughout the framing, in accordance with the particular building plan or blueprints. The placement of outlets varies according to the job. The wall board, or other sheet like wall surface material, is conventionally placed over the framing after all wiring outlet and conduit boxes have been installed. Prior to installation there is no way to predict where the outlet boxes will be relative to the wall board, so custom fitting at the job site is the norm. Thus all wallboards are configured at the particular job site prior to installation. Suitable access holes must be cut in the panels to expose the outlet boxes secured to the framing.
The access openings must be accurately positioned cut to properly expose and align with the outlet and junction boxes after the drywall is installed. In other words, the drywall applicator must accurately factor in the number, position and shape of the outlet and junction boxes that will be "covered" by the wallboard panels he or she is installing. The relative position of the access openings must be carefully determined. The access holes may be cut before or after the wallboard is nailed into position.
Some installers cut access openings in the wallboard prior to nailing the panels to the frame. When access openings are formed before the drywall is installed, very careful measurements, and painstaking devotion to detail, are required. Often the panel must be placed, measured and scribed, cut, and then replaced and remeasured a number of times before the access holes are properly formed and aligned. The position and placement of each outlet box must be carefully determined, and this information must be carefully transferred to the wall board panel prior to cutting.
Others cut the access holes after nailing the premarked panel in place. Some installers cut the required access holes with a drywall knife. Some use a hammer and chisel or a keyhole saw. Care must be taken not to damage the outlet box or the area surrounding the access hole when the relatively crude cuts are made. In any event, the attainment of a high quality fit and finish requires considerable patience and skill. Those drywall applicators who are most able to achieve the desired quality are in great demand.
However, it is difficult and time consuming to repetitively make proper measurements. Even skilled craftsmen make mistakes from time to time, and sheet materials are wasted, and valuable time is lost. Electricians sometimes complain about access hole alignment, even where careful measurements have been made. Sometimes modifications to the drywall must be made by the electrician to accommodate dimensional misalignment. To remedy these problems a number of devices have been proposed in the prior art to make the marking and cutting of access orifices in wall board or other sheet like materials easier and more accurate. Devices have been proposed that can be mounted on the outlet boxes to position templates to guide cutting tools for forming the access opening. Examples are seen in U.S. Pat. Nos. 2,775,812, 2,788,151, 3,733,707, 3,823,754, 3,888,013, 3,733,707, 4,359,302, 4,730,395, 4,335,511, 4,059,905 and others.
Some prior art templates mount at least temporarily on the outlet boxes and present a projection that mark and/or penetrate the wall panel to provide a marking. Still, some measuring is required for reasonable accuracy. This technique has proven versatile with relatively soft gypsum wall board. Paneling made of harder materials are more difficult to penetrate with the template locating member. Many template tool are relatively large and cumbersome, The sharp, projecting blades or prongs are dangerous to transport, and sometimes difficult to use. It would be far better to provide a marking system comprised of small, disposable clip on members that easily mark the proper dimensions, and once used, can be discarded (i.e., removed and thrown away or left concealed behind the finished wall board.)